do power steering pumps with clutches exist?

Has any manufacturer tried fitting a clutch to a power steering pump in order to prevent the pump from running when the driver is not steering much? I would envision the clutch being engaged when there was any movement in the rack input shaft, and then when there was enough twist, the valves would direct fluid (now under pressure since the pump was engaged) to the appropriate side as usual. Just curious if anyone has seen a system like this or knows why it is impractical (perhaps the gas savings are neglectable).

Reply to
Ryan Underwood
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My Integra has variably assisted steering (more car speed, less boost).

Assist control is effected through pressure modulation, the modulated pressure being measured against a constant reference pressure that is present in the system. The primary input seems to be a small fluid pump that is incorporated into the speedometer drive gear housing.

Do any air-conditioning systems work this way?

Reply to
Hugo Schmeisser

That device is more like a governor than a pump.

Most A/C systems cycle their compressor off either when the evaporator temp sensor reaches a preset temp or when the pressure cycling switch reaches a preset pressure in the low side of the system.

A few systems remain engaged constantly but they control the flow of refrigerant through the low side at a set pressure. Even these types have the capability to shut off the compressor in the event of loss of refrigerant or excessively high pressure.

Toyota MDT in MO

Reply to
Comboverfish

Don't forget the variable displacement A/C compressors. These are constantly engaged, but vary the displacement of the compressor to match the demand. From

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: "V-5 Compressors

"The first volume-produced variable displacement compressor, the five-piston V-5 automatically adjusts displacement to match the vehicle's air conditioning demand. A control valve in the V-5's rear head senses evaporator load and automatically changes displacement to match that load. Unlike cycling clutch air conditioning systems, Delphi's V-5's continuous displacement feature results in smooth, continuous compressor operation without any clutch cycling, improving air conditioning performance and fuel economy."

Toyota (and most other manufacturers) is also planning on deploying variable displacement compressors.

Ed

Reply to
C. E. White

Impractical because too slow to respond, I imagine.

Reply to
Misterbeets

Yes, that's what I meant by "primary input". I guess I should have said "primary SIGNAL input". The hoses leading to that pump are tiny and carry low pressure. The pump is there solely to drive a spring-loaded pressure regulation system within the main pump.

Would a power steering system with a clutch need a pressure regulation system anyway?

Reply to
Hugo Schmeisser

When you aren't steering, there is little load on the power steering pump. It is mostly just circulating the oil. If you actually tried to implement a clutching system, it would be constantly switching in and out, and probably would result in steering hesitation because of the delay between sensing steering effort, clutch engagement, and pressure delivery.

My Vue has electrically operated power steering. I think this is probably the wave of the future. Whenever the manufacturers make the jump to higher voltage systems (48 volts?), a lot of accessories will change over from belt drive to electric drive.

Ed

Reply to
C. E. White

Seems like a lot of complexity for a little benefit. However, before I actually read your post (but had read the subject line) I was immediately reminded of the Studebaker mechanical power steering introduced in the early 50's. AFAIK all of the vehicles so fitted were recalled and retrofitted with Saginaw hydraulic setups however, and info. on this system is difficult to find. I haven't tried Googling for it, but if you have any mechanical curiosity, it might be a good read if you can find a description of it.

Now I am trying to remember where *I* read an article on it... I think it was probably an old back issue of Turning Wheels (Studebaker club magazine) I do know I've seen at least one photograph of such a system

- where you'd expect to see a PS pump, there's a belt-driven pulley with a U-jointed shaft going straight into the steering box. I believe that a system of clutches inside the steering box applied or released depending on what was required to provide the assist. I have absolutely no idea how well it worked, but apparently not well enough.

nate

(with a '55 coupe, with the early Saginaw hydraulic box. Did you know there's seperate sections of the steering box, one lubricated by the power section's fluid, and one lubricated by conventional gear oil? Neither did my car's previous owner!)

Reply to
N8N

Don't worry, I didn't ;) The V5 has been around for a while, and, though implimented differently than typical EVR EPR STV POA etc. systems, it still accomplishes a similar outcome. It is a good idea, but seems to yield little real world benefit IMHO.

Toyota MDT in MO

Reply to
Comboverfish

Also, '55-'57 (and earlier) Chevy's had a *part-time* power steering; I believe you had to exert a certain amount of force on the steering wheel for the ps to give any assist. Felt much like conventional steering on the road, but like p-steering when turning corners/parallel parking. Did a nice job, other than leaking fluid, IIRC. s

Reply to
sdlomi2

but don't you wish you could?

Except to generate aggravation among people who a) own cars equipped with a V5 compressor and b) the mechanics who get yelled at by car owners because the damn things don't last to the end of the driveway.

When they are working, variable-displacement compressors achieve the same result as the Evaporator Pressure Regulator type systems you mentioned first- they take much of the load off the compressor input shaft, but leave the shaft spinning. EPR systems do it by allowing the compressor to pull against a partial vacuum (caused by the EPR valve closing and limiting refrigerant return flow from the evaporator). Much simpler than mechanically altering the displacement of a compressor. The drawback to EPR systems is that they begin throttling down the cooling capacity at relatively high evaporator temperatures (45-50 degrees F) which slows down the rate at which the system can cool down a hot car. Cycling clutch systems hold the evap temp right at 35-40 degrees F by cycling the compressor on when the evap temp hits ~40, and off when it hits ~38 as needed. More mechanical wear, and you can feel the compressor cycling- but better overall cooling.

Reply to
Steve

Good observations. I guess a big reason the variable displacement units were used was to eliminate the "feel" of clutch cycling. But God forbid you don't take every precaution in the book and use the exact oil in a V5 while servicing a GM. And good luck with the R134a conversion on one of those...

Toyota MDT in MO

Reply to
Comboverfish

Well the idea must not be all bad. Toyota is developing (with Denso) similar compressors.

Ed

Reply to
C. E. White

You actually have it backwards. When you are not steering, the oil circulates freely. When you steer, you essentially put a blockage in the return line, which creates pressure in the system and applies it to the appropriate side of the hydralic cylinder. Normally the only time oil passes throught the relif valve is when you crank the steering over against the stop and hold it there. This essentially blocks the return line while the stops prevents the steering gear from moving and reopening the return line. This is when you get the squealing noise (caused by oil passing through the relief valve).

Ed

Reply to
C. E. White

The variable displacement idea is fine. Luckily, Nippon Denso has a history of engineering vastly more durable automotive components than Delco(phi). Of course, this observation has been formed from years of wrenching, reading, and talking to peers, so it is only opinion. If Denso (Nippon or USA) supplies a VDC, I'm sure it will be a quality product.

Toyota MDT in MO

Reply to
Comboverfish

Denso's track record is a *little* better than GMs when it comes to being able to produce a reliable compressor. I'd have more confidence if it were Sanden, but Denso's not a bad bet. Now if York were still a leader in automotive compressor industry, I'll bet they could do it with their eyes closed.

Reply to
Steve

Yeah, if you ignore the early versions of the NipponDenso C-171 ;-)

To be fair, the later versions are as good as a Sanden.

Reply to
Steve

Yeah, but few auto manufacturers are specing out one foot cube sized compressors these days :)

BTW, see my response to the dickweed known simply as * further down this thread.

Toyota MDT in MO

Reply to
Comboverfish

Restricting the hose with the end of your thumb will increase the flow RATE at that point, but the flow VOLUME is the same. The pressure on your thumb corresponds to the amount of increase in the flow rate that is necessary to get past the restriction.

Reply to
Ryan Underwood

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